1. Field of the Invention
This invention pertains to concentrated protein formulations with reduced viscosity, which are particularly suitable for subcutaneous administration. The invention further concerns a method of reducing viscosity of concentrated protein formulations.
2. Description of the Related Art
In the past ten years, advances in biotechnology have made it possible to produce a variety of proteins for pharmaceutical applications using recombinant DNA techniques. Because proteins are larger and more complex than traditional organic and inorganic drugs (i.e. possessing multiple functional groups in addition to complex three-dimensional structures), the formulation of such proteins poses special problems. One of the problems is the elevated viscosity values of protein formulations, especially at high concentration. The delivery of high protein concentration is often required for subcutaneous administration due to the volume limitations (≦1.5 ml) and dose requirements (usually ≧50 mg, preferably ≧100 mg). For example, if a protein is to be administered to patients at 2 mg/kg on a weekly basis, the average weekly dose will be 130 mg considering 65 kg as the average weight of patients. Since injection volumes of more than 1.5 ml are not well tolerated for subcutaneous administration, the protein concentration for a weekly subcutaneous administration would have to be approximately 100 mg/ml (130 mg protein in less than 1.5 ml volume). However, highly concentrated protein formulations pose several problems. One problem is the tendency of proteins to form particulates during processing and/or storage, which makes manipulation during further processing difficult. In the case of reconstituted liquid formulations, this is usually circumvented by adding a suitable surfactant (e.g. a polysorbate) during lyophilization or after lyophilization while reconstituting the formulation. Although surfactants have been shown to significantly reduce the degree of particulate formation of proteins, they do not address another problem associated with manipulating and administering concentrated protein formulations. Proteins tend to form viscous solutions at high concentration because of their macromolecular nature and potential for intermolecular interactions. Moreover, many proteins are often lyophilized in the presence of large amounts of lyoprotectants, such as sugar to maintain their stability. The sugar can enhance the intermolecular interactions and increase the viscosity. Highly viscous formulations are difficult to manufacture, draw into a syringe and inject subcutaneously. The use of force in manipulating the viscous formulations leads to excessive frothing, and the resultant detergent-like action of froth has the potential to denature and inactivate the therapeutically active protein. Moreover, viscous solution increases the back-pressure during UF/DF process and makes recovery of protein difficult. This can result in considerable loss of protein product. Satisfactory solution of this problem is lacking in the prior art. Therefore, there is a need to develop a method of reducing the viscosity of a formulation containing high concentration of protein.
Stable isotonic lyophilized protein formulations are disclosed in PCT publication WO 97/04801, published on Feb. 13, 1997, the entire disclosure of which is hereby expressly incorporated by reference. The disclosed lyophilized formulations can be reconstituted to generate high protein-concentration liquid formulations without apparent loss of stability. However, the potential issues associated with the high viscosity of the reconstituted formulations are not addressed.
Applicants have discovered that the preparation of proteinaceous, lyophilized formulation with 100 mM NaCl diluent can result in a slightly hypertonic solution. It had been previously believed that pharmaceutical formulations must be maintained at physiological pH and be isotonic. This belief was based at least in part on the perception that the administration of hypertonic formulation could lead to dehydration and therefore could damage the tissue at the site of injection. However, the belief of the requirement for absolute isotonicity of a pharmaceutical formulation may not be well-founded. For example, Zietkiewicz et al., Grzyby Drozdzopodobne 23: 869-870 (1971) have shown that absolute isotonicity of the drugs is not necessary. It was found to be sufficient to avoid the drug solutions that exceed the critical limits of hypertonicity. For example, tissue damage was observed only when hypertonic solution of 1300 mOsmol/Kg (˜650 mM NaCl) or higher was administered subcutaneously or intramuscularly to experimental animals. As a result, formulations which are slightly hypertonic, or outside of the physiological pH range do not appear to present a risk of tissue damage at the site of administration.
Applicants have further found that proteinaceous solutions having a lowered (4.0-5.3) or elevated (6.5-12.0) pH was also effective at reducing the viscosity of high concentration protein formulations.
The present invention is directed to providing a high concentration protein formulation with reduced viscosity, which is easy to handle and is suitable for subcutaneous administration. The present invention is further directed to providing a method of reducing viscosity of concentrated protein formulations.